U.S. patent application number 11/640322 was filed with the patent office on 2007-05-03 for electrophoretic display sheet, electrophoretic display, electric apparatus, and method of manufacturing electrophoretic display sheet.
This patent application is currently assigned to Seiko Epson Corporation. Invention is credited to Sadao Kanbe.
Application Number | 20070097490 11/640322 |
Document ID | / |
Family ID | 37693992 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070097490 |
Kind Code |
A1 |
Kanbe; Sadao |
May 3, 2007 |
Electrophoretic display sheet, electrophoretic display, electric
apparatus, and method of manufacturing electrophoretic display
sheet
Abstract
A method of manufacturing an electrophoretic display sheet that
includes: applying a mixture of a plurality of microcapsules and a
binder on a substrate, the substrate having a first contact angle
.theta.1 between a reference liquid, each of the microcapsules
having a second contact angle .theta.2 between the reference
liquid, the binder having a third contact angle .theta.3 between
the reference liquid, the .theta.1, the .theta.2, and the .theta.3
having a relationship of .theta.3>.theta.2>.theta.1; and
evaporating the mixture to form an electrophoretic layer on the
substrate, the electrophoretic layer including the plurality of the
microcapsules.
Inventors: |
Kanbe; Sadao; (Suwa-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Seiko Epson Corporation
Tokyo
JP
|
Family ID: |
37693992 |
Appl. No.: |
11/640322 |
Filed: |
December 18, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11423088 |
Jun 8, 2006 |
7193770 |
|
|
11640322 |
Dec 18, 2006 |
|
|
|
Current U.S.
Class: |
359/296 |
Current CPC
Class: |
G02F 1/16757 20190101;
G02F 1/167 20130101 |
Class at
Publication: |
359/296 |
International
Class: |
G02B 26/00 20060101
G02B026/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2005 |
JP |
2005-220206 |
Oct 14, 2005 |
JP |
2005-300928 |
Claims
1. A method of manufacturing an electrophoretic display sheet,
comprising: applying a mixture of a plurality of microcapsules and
a binder on a substrate, the substrate having a first contact angle
.theta.1 between a reference liquid, each of the microcapsules
having a second contact angle .theta.2 between the reference
liquid, the binder having a third contact angle .theta.3 between
the reference liquid, the .theta.1, the .theta.2, and the .theta.3
having a relationship of .theta.3>.theta.2>.theta.1; and
evaporating the mixture to form an electrophoretic layer on the
substrate, the electrophoretic layer including the plurality of the
microcapsules.
2. A method of manufacturing an electrophoretic display sheet
according to claim 1, including: applying lyophilic processing to
lessen the angle of contact of the substrate relating to the
reference liquid, prior to coating the mixture in the manufacturing
process of the electrophoretic display sheet.
3. The manufacturing process of the electrophoretic display sheet
according to claim 1, wherein the reference liquid is water in the
manufacturing process of the electrophoretic display sheet.
4. A method of manufacturing an electrophoretic display comprising
the method of manufacturing the electrophoretic display sheet
according to claim 1.
5. A method of manufacturing an electric apparatus comprising the
method of manufacturing the electrophoretic display according to
claim 4.
Description
[0001] This is a Division of application Ser. No. 11/423,088 filed
Jun. 8, 2006. The disclosure of the prior application is hereby
incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Technical Field
[0003] The invention relates to an electrophoretic display, which
makes use of movement of charged molecules in an electric field for
displaying information, and its manufacturing process.
[0004] 2. Related Art
[0005] Broadly speaking, an electrophoretic display is constituted
by an electrophoretic layer provided between a pixel electrode
substrate and a common electrode substrate. The electrophoretic
layer includes more than one kind of colored electrophoretic
particle and a liquid phase disperse medium, which makes the
electrophoretic particle movable, and is sealed between the both
substrates. And when a pixel signal (voltage) corresponding to
two-dimensional image information is applied between each pixel
electrode of the pixel electrode substrate and the common electrode
substrate, a position of the electrophoretic particle is set
corresponding to a level of the pixel signal, whereby an image is
formed. As referenced above, the electrophoretic particles move in
the disperse medium, while if the electrophoretic display tilts,
uneven distribution (unbalanced) of the electrophoretic particles
can occur. To prevent this, the electrophoretic layer is divided by
partition members or a plurality of electrophoretic particles and
the disperse medium are wrapped in a wall member and made into
microcapsules. For example, U.S. Pat. No. 5,961,804 shows an
example in which the electrophoretic layer of the electrophoretic
display is formed by micro-encapsulation.
[0006] U.S. Pat. No. 5,961,804 is an example of related art.
[0007] In a case where the electrophoretic layer is formed by
micro-encapsulation, to form an intricate image, the microcapsules
need to be compactly coated all over the substrate without a gap
such that a film needs to be made without a gap while microcapsules
are tightly in contact with one another.
[0008] However, in a currently available technique of forming the
electrophoretic layer through the microcapsules, a liquid in which
the microcapsules are dispersed is coated on the substrate and
dried, thus making it easy to produce gaps among the microcapsules.
It is difficult to adjust concentration of the microcapsules in the
disperse liquid as well as coating work so as to prevent such
phenomenon.
[0009] Now, it may be conceived to coat the disperse liquid in
advance, so that the electrophoretic layer becomes a thick film in
advance, while this is held between two electrode substrates to
push the microcapsule layer inside, thereby sticking one
microcapsule to another very closely. However, such arrangement
causes residual stress (restoring force) to generate inside the
microcapsule layer, and exfoliation and deformation tend to occur
between the electrophoretic layer and the electrode substrate. In
case of a large-sized substrate, overall pressuring (holding)
itself is difficult to be applied. Further, if the disperse liquid
solidifies, deformation is difficult to occur, hence, before the
disperse liquid dries up, the electrode substrates need to be glued
together.
SUMMARY
[0010] An advantage of the invention is to provide an
electrophoretic display sheet and an electrophoretic display which
enable an electrophoretic layer, in which microcapsules adhere
closely together, to be formed on an electrode substrate to provide
for intricate image display.
[0011] A further advantage of the invention is to provide a
manufacturing process of an electrophoretic display sheet and an
electrophoretic display which enable an electrophoretic layer, in
which the microcapsules adhere closely together, to be formed more
easily on the electrode substrate.
[0012] According to a first aspect of the invention, an
electrophoretic display sheet of the invention includes: a
substrate; and an electrophoretic layer made into a film on the
substrate, including a plurality of microcapsules, in which an
electrophoretic disperse medium containing at least one kind of
electrophoretic particle is sealed, and a binder bonding or fixing
the microcapsules to one another, wherein a degree of affinity of
the substrate, the microcapsule, and the binder is respectively
formed such as to increase in order of the microcapsule, the binder
and the substrate.
[0013] At this point, the electrophoretic display sheet is that
which is made up of an electrophoretic layer formed on the
substrate. Further, the affinity is determined by an angle of
contact between the substrate and a reference liquid, the angle of
contact between the microcapsule and the reference liquid, and the
angle of contact between the binder and the reference liquid. The
reference liquid is, for example, water, but not limited to this,
and a selection can be made as appropriate.
[0014] According to such constitution, when the binder entwined
around the microcapsules attempt to spread along the substrate, it
operates to extend the microcapsules at a broader width along the
substrate. As each microcapsule spreads on the substrate, adhesion
among the microcapsules becomes tighter, thereby making it possible
to obtain an electrophoretic display sheet having an
electrophoretic layer without a gap between one microcapsule and
another. This enables an electrophoretic display capable of forming
intricate imagery to be obtained..
[0015] According to a second aspect of the invention, the
electrophoretic display sheet includes a substrate; and an
electrophoretic layer made into a film on the substrate, including
a plurality of microcapsules, each of the plurality of
microcapsules including an electrophoretic disperse medium and at
least one kind of electrophoretic particle, and a binder bonding
the microcapsules to one another, wherein the affinity between the
binder and the substrate and the affinity between the binder and
the microcapsule are set to be higher than the affinity between the
microcapsule and the substrates.
[0016] Even in such constitution, when the affinitive binder
entwined around the microcapsules attempt to spread along the
substrate, it operates to extend the microcapsules at a broader
width along the substrate. As each microcapsule spreads on the
substrate, adhesion among the microcapsules becomes tighter,
thereby making it possible to obtain an electrophoretic display
sheet having an electrophoretic layer without a gap between one
microcapsule and another. This enables an electrophoretic display
capable of forming intricate imagery to be obtained.
[0017] Preferably, the electrophoretic layer has a planar structure
with one microcapsule tightly adhering to another due to the
affinity of the binder. This makes it possible to obtain an
electrophoretic display sheet having an electrophoretic layer with
the microcapsules tightly adhering to one another without a
gap.
[0018] Preferably, the binder includes, for example, a
water-soluble resin. This makes it possible, for example, for the
affinity between the wall member of the water-soluble microcapsule
and the binder to improve significantly, so that when the binder
attempts to spread over the substrate, the microcapsules also
spread because of wettability of the binder and are fixed on the
substrate.
[0019] Preferably, the wall member of the microcapsule includes a
water-soluble resin. This enables the affinity among the
microcapsule, for example, the binder including the water-soluble
resin and the substrate to improve significantly. When the binder
attempts to spread on the substrate, the microcapsules also spread
due to surface tension of the binder and are fixed on the
substrate.
[0020] Further, an electrophoretic display according to the
invention includes: a first and a second substrates which are
placed mutually opposite to each other, and on each opposite
surface of which electrodes are respectively formed; and an
electrophoretic layer made into a film on the first substrate,
including a plurality of microcapsules, in which an electrophoretic
disperse medium containing at least one kind of electrophoretic
particle is sealed, and a binder bonding the microcapsules to one
another, wherein a degree of affinity of the first substrate, the
microcapsule, and the binder is respectively formed such as to
increase in the order of the microcapsule, the binder and the first
substrate.
[0021] According to such constitution, when the binder entwined
around the microcapsules attempt to spread along the first
substrate, it operates to extend the microcapsules at a broader
width along the substrate. As each microcapsule spreads on the
first substrate, adhesion among the microcapsules becomes tighter,
thereby making it possible to obtain an electrophoretic display
layer with the microcapsules packed with no gap between one
microcapsule and another. As a result, an electrophoretic display
capable of forming intricate imagery can be obtained.
[0022] According to a third aspect of the invention, a
manufacturing process of an electrophoretic display of the
invention includes: coating, on a substrate which is a first angle
of contact relating to a reference liquid, a mixture of a plurality
of microcapsules which is a second angle of contact relating to the
reference liquid, and the binder which is a third angle of contact
relating to the reference liquid; and drying the substrate coated
with the mixture and forming an electrophoretic layer including the
plurality of microcapsules, wherein a relationship of
.theta.3>.theta.2>.theta.1 holds where the first angle of
contact is .theta.1, the second angle of contact is .theta.2, and
the third angle of contact is .theta.3.
[0023] Preferably, applying lyophilic processing to the substrate
prior to coating the mixture is included.
[0024] Preferably, applying lyophilic processing includes plasma
processing and ozone processing.
[0025] Through such constitution, it is possible to form an
electro-phoretic layer in which the microcapsules adhere closely
together. An electrophoretic display sheet (electrophoretic
display) of high contrast by curbing uneven display can be
obtained. Further, since no external pressure is applied to between
the substrates as in the currently available technique, residual
stress of the microcapsules (or restoring force) contributes to not
generating exfoliation and distortion between the substrates.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] The invention will be described with reference to the
accompanying drawings, wherein like numbers refer to like
elements.
[0027] FIG. 1 is a longitudinal section showing an embodiment an
electrophoretic display according to the invention.
[0028] FIG. 2 presents schedule drawings to explain a manufacturing
process of an electrophoretic display shown in FIG. 1.
[0029] FIG. 3 presents explanatory diagrams to explain operations
in an embodiment of an electrophoretic display according to the
invention.
[0030] FIG. 4 is an explanatory diagram to explain a state of an
electrophoretic layer of an electrophoretic display according to
the invention.
[0031] FIG. 5 is an explanatory diagram to explain characteristics
(angle of contact) of materials in a manufacturing process of an
electrophoretic display according to the invention.
[0032] FIG. 6 presents diagrams to show examples of electronic
equipment to which an electrophoretic display of the invention is
applicable.
[0033] FIG. 7 presents diagrams to show examples of electronic
equipment to which an electrophoretic display of the invention is
applicable.
[0034] FIG. 8 is a longitudinal section of an electrophoretic
display as a comparison example.
DESCRIPTION OF THE EMBODIMENTS
[0035] Embodiments of the invention will be described as follows
with reference to the drawings.
[0036] Electrophoretic Display Sheet and Electrophoretic
Display
[0037] FIG. 1 is a longitudinal section of an embodiment of an
electrophoretic display according to the invention.
[0038] In this working example, a common electrode substrate 10 as
a substrate and an electrophoretic layer 30 formed thereon
constitute an electrophoretic display sheet. However, the
electrophoretic layer 30 may be formed on a pixel electrode
substrate 20, and these may be used as an electrophoretic display
sheet. In this case, the same result can be obtained even if the
common electrode substrate 10 is replaced by the pixel electrode
substrate 20.
[0039] An electrophoretic display 1 consists of the common
electrode substrate 10 which formed a common electrode 12 on a
substrate 11, an electrophoretic layer 30 which is formed by
utilizing surface tension of a binder 36, as explained later, on
microcapsules 35 including electrophoretic particles 31, a
plurality of drive elements, which are respectively driving a
plurality of pixel electrodes arrayed in a matrix pattern on the
substrate 21 and each pixel, and a pixel electrode substrate 20
constituted by forming a pixel electrode circuit 22 including a
plurality of wiring and the like.
[0040] The common electrode substrate 10 and the pixel electrode
substrate 20 are placed opposite to each other in a manner of
sandwiching the electrophoretic layer 30. In this working example,
since the microcapsules 35 of the electrophoretic layer 30 are
packed without a gap in a stone wall shape or a tile shape as
expeditiously as possible, for example, the affinity of the
microcapsule 35, the binder 36, and the common electrode substrate
10 is controlled (or set).
[0041] For example, when water is set as a reference liquid for
measuring the affinity of each material and each substrate, the
microcapsule 35, the binder 36, and the common electrode substrate
10 have respective affinity to water. Further, each material and
each substrate are selected so that a degree of affinity to water
increases in order of the microcapsule 35, the binder 36, and the
common electrode substrate 10.
[0042] Or materials and substrates are selected so that the
affinity between the binder 36 and the common electrode substrate
10 and the affinity between the binder 36 and the microcapsule 36
become larger than the affinity between the microcapsule 35 and the
common electrode substrate 10.
[0043] Large affinity herein means a small difference of an angle
of contact relating to the reference liquid. For example, when
there is a large lyophilic property of the substrate and the
microcapsule 35 (in the strict sense of the word, a wall member 33
which is a constituent element of the microcapsule 35), it means a
small difference (A-B) between the angle of contact (A) of water to
the substrate and the angle of contact (B) of water to the wall
member 33.
[0044] Further, when there is a large lyophilic property between
the microcapsule 35 and the binder 36, it means a small difference
between the angle of contact of water to the wall member 33 and the
angle of contact of water to the binder 36.
[0045] The common electrode substrate 10 forms a common electrode
12 in a layer on the substrate 11.
[0046] A pixel electrode substrate 20 forms in a layer, on the
substrate 21, a pixel electrode circuit layer 22 which includes
pixel electrodes in a matrix pattern corresponding to a number of
pixels and active elements.
[0047] It is preferable that the pixel and part of the wiring of
the pixel electrode circuit layer 22 are a transparent electrode
film such as ITO and that a drive element is an active element such
as a thin film transistor (TFT).
[0048] Substrates 11 and 21 employed for the electrode substrate
have, as a raw material, a plastic material in a sheet shape, such
as glass or polyethylene terephthalate (PET). Further, its
thickness (average) is set as appropriate depending on respective
components and usage, and there is no particular limitation. For
example, in a case where a substrate having flexibility is to be
used, its thickness is preferably on the order of 20 to 500 .mu.m,
and more preferably, on the order of 25 to 250 .mu.m. This makes it
possible to proceed with miniaturizing the electrophoretic display
1 (especially, making into a thin type) while maintaining harmony
between flexibility and strength.
[0049] For the common electrode 12, that which has transparency of
light with ITO, ZnO and the like as its material, preferably, what
is virtually transparent (colorless and transparent, colored
transparent or semitransparent) is acceptable. This enables status
of an electrophoretic particle 31 in an electrophoretic disperse
liquid 32 to be explained later, that is, information (image)
displayed in the electrophoretic display 1 to be easily
recognizable through visual examination.
[0050] Further, its thickness (average) is set as appropriate
depending on components, usage, and the like. There is no
particular limitation. But preferably it is on the order of 0.05 to
10 .mu.m, more preferably on the order of 0.05 to 5 .mu.m.
[0051] With respect to the common electrode substrate 10, to secure
affinity with the binder 36 and the microcapsule 35 (wall member
33) to be explained later, lyophilic processing such as plasma
irradiation and ozone irradiation is suitable. Note that if the
substrate has the affinity originally desired, it is not
particularly necessary to apply lyophilic processing.
[0052] The electrophoretic layer 30 is a single layer (not
overlaying in a thickness direction but one by one) in which a
plurality of microcapsules 35 are arrayed in a row vertically and
horizontally without mutual gaps through the binder 36, and it is
made into a film on the common electrode substrate 10. This enables
the electrophoretic display 1 to exhibit better display
performance.
[0053] This microcapsule 35 is constituted by wrapping the
electrophoretic disperse liquid 34 with the wall member 33. As the
component of the wall member 33, for example, that which has the
water-soluble characteristic can be used. Take, for instance, a
compound of gum arabic and gelatin as well as various resin
materials such as a urethane resin and a melamine resin. Of these,
one kind or a combination of more than two kinds can be used.
[0054] It is preferable for such microcapsules 35 to have an
approximately uniform size. This enables the electrophoretic
display 1 to have uniform quality of display and to exhibit better
display performance.
[0055] The electrophoretic disperse liquid 34 is obtained by
dispersing (suspension) with a dispersing method such as stirring
at least one kind of electrophoretic particle 31 with a liquid
disperse medium 32.
[0056] So long as electrophoretic particle 31 has a property of
electrification and is a molecule which is electrophoretic in the
liquid phase disperse medium 32 through action of the electric
field, there is no special limitation. Pigment molecules such as
titanium oxide, resin molecules such as an acrylic resin, or at
least one kind of these compound molecules may be suitably
used.
[0057] An average particle size (diameter of average particle in
volume) of the electrophoretic particle 31 is preferably on the
order of 0.1 to 10 .mu.m. If the average particle size of the
electrophoretic particle 31 is too small, a sufficient contrast
ratio cannot be obtained mainly in a visible light region. As a
result, it is considered that a display contrast of the
electrophoretic display 1 may drop.
[0058] On the other hand, if the average particle size of the
electrophoretic particle 31 is too large, depending on factors such
as its kind, it tends to precipitate, so that deterioration of
display quality of the electrophoretic display 1 may be
considered.
[0059] As the liquid phase disperse medium 32, that which has
comparatively high insulating property such as dodecyl benzene is
suitably used.
[0060] Further, as necessary, a disperse and charge control agent
such as a titanium type coupling agent and an aluminum type
coupling agent may be added into the liquid phase disperse medium
32 (electrophoretic disperse liquid 34).
[0061] Still further, as necessary, various dyes such as an
anthraquinone dye and an azo dye may be dissolved in the liquid
phase disperse medium 32.
[0062] Of resin materials excelling in affinity with the common
electrode substrate 10 and the capsule wall member 33 (microcapsule
35) and excelling in insulating property, for example, one kind or
a combination of more than two kinds of water-soluble high molecule
materials such as polyvinyl alcohol and cationic cellulose may be
suitably used.
[0063] In the working example, there is shown an embodiment which
is a film of the electrophoretic layer 30 made on the common
electrode substrate 10. The film may be made on the pixel electrode
substrate 20, and in that case, lyphilic processing is applied onto
the pixel electrode substrate 20.
[0064] In the constitution referenced above, when a voltage is
impressed between the pixel electrode circuit layer 22 (of a pixel
electrode) and the common electrode 12, an electric field generates
therebetween. This electric field causes the electrophoretic
particle 31 to move inside the microcapsule 35 and an image is
displayed.
[0065] In forming the electrophoretic layer 30 as referenced above,
the affinity among the microcapsule 35, the binder 36, and the
common electrode substrate 10 are utilized as explained later.
Accordingly, by means of the surface tension of the binder 36, each
microcapsule 35 is deformed into the common electrode substrate 10
side and film-making free from any gap is made between one
microcapsule to another. The microcapsule layer is fixed on the
common electrode substrate 10 by the binder 36.
[0066] Consequently, without pressuring between the substrates and
distorting the microcapsules 35 like the currently available
technique, and also without being concerned about quality
deterioration such as exfoliation of the common electrode substrate
10 and uneven display due to residual stress (or restoring force)
of the microcapsules 35, it is possible to obtain, through a
simpler manufacturing process, the electrophoretic display 1 which
provides high image quality.
[0067] FIG. 4 schematically shows an example (plan view) of a state
of the microcapsules 35 of the electrophoretic layer 30 in the
working example as viewed from above. It is seen that the
microcapsules 35 are mutually formed in the shape of the stone
walls or the tiles with very few gaps among the microcapsules.
[0068] FIG. 8 shows a comparison example. Elements in this figure
corresponding to elements in FIG. 1 are given like numbers and
description of such elements is omitted.
[0069] In the comparison examples, the electrophoretic layer is
simply coated on one of the two substrates 10 and 20, and a
structure is such as to sandwich it with two substrates.
Consequently, there is a gap between one microcapsule 35 to
another.
[0070] By comparison to the electrophoretic display of this
comparison example, according to the constitution of the working
example, a film is made while the microcapsules 35 forming the
electrophoretic layer are being packed with no gaps among
themselves, hence, no uneven display quality is produced thus to
enable high resolution image display to be made.
[0071] Further, in the comparison example, if an attempt should be
made to array the microcapsules tightly without a gap by changing
the shape of the microcapsules as in this working example, it is
necessary to pressure externally the substrates themselves, which
sandwich the electrophoretic layer 30 including the microcapsules,
so as to deform the microcapsules. However, that is not necessary
in this working example, so there are no chances such as substrate
exfoliation and deformation due to residual stress of the
microcapsules which could generate in case of pressuring, and high
resolution image display can be stably obtained.
[0072] Manufacturing Process
[0073] FIG. 2 is a presentation with scheduling drawings of a
manufacturing process of the electrophoretic display
(electrophoretic display sheet) shown in FIG. 1.
[0074] First, as shown in FIG. 2A, in process A, the common
electrode 12 is formed on the substrate 11 and the common electrode
substrate 10 is manufactured. After the formation, lyophilic
processing is applied to a substrate surface of an electrode side
of the common electrode substrate 10. For lyophilic processing,
plasma irradiation, ozone irradiation and the like are suitable. By
carrying out such processing, an electrode surface of ITO and the
like of the substrate surface is activated, thus improving
wettability.
[0075] Next, as shown in FIG. 2B, in process B, a mixture of
pre-mixed microcapsules 35 and the binder 36 is coated on the
common electrode substrate 10 (to be more specific, on the common
electrode 12) so that there is uniform coating.
[0076] As a coating method, a doctor blade method, a spin coat
method and the like are suitable. As referenced above, the
microcapsule 35, the binder 36, and the common electrode substrate
10 have respective affinity. Further, the material and the
substrate are selected or formed such that the degree of affinity
may increase in the order of the microcapsule 35, the binder 36,
and the common electrode substrate 10.
[0077] As shown in FIG. 2C, in process C, the mixture of the
micro-capsules 35 and the binder 26 uniformly coated in process B
is dried for about 10 minutes at a temperature of 90.degree. C.,
and the microcapsules 35 are made into a film without gap on the
common electrode substrate 10 through the binder 36 and fixed.
[0078] FIG. 3 are explanatory diagrams to explain operation when
the microcapsules 35 are made into a film on the common electrode
substrate 10. FIG. 3A shows a state where the mixture of
microcapsules 35 and the binder 36 is coated on the common
electrode substrate 10. As referenced above, the microcapsule 35,
the binder 36, and the common electrode substrate 10 have
respective affinity and are formed so that the degree of affinity
increases in the order of the microcapsule 35, the binder 36, and
the common electrode substrate 10.
[0079] Or the affinity between the binder 36 and the common
electrode substrate 10 and the affinity between the binder 36 and
the microcapsule 35 are set to be higher than the affinity between
the microcapsule 35 and the common electrode substrate 10.
[0080] For example, when water is set as the reference liquid, it
is set up such that a relationship .theta.3>.theta.2>.theta.1
holds where the angle of contact between the common electrode
substrate 10 subjected to lyophilic processing and water is
.theta.1, the angle of contact between the material of the binder
36 and water is .theta.2, and the angle of contact between the
material of the microcapsule 35 and water is .theta.3.
[0081] At this point, as shown in the explanatory diagram of FIG.
5, the angle of contact .theta. is an angle formed by a tangential
line drawn from a point of contact between the liquid and a solid
into a perpendicular plane of the solid when the liquid is in
contact with the solid surface. It is also called a "wet angle." In
case of being wettable, the angle of contact becomes an acute
angle, while in case of being not wettable, the angle of contact
becomes an obtuse angle.
[0082] In the working example, for example, there are
.theta.1=3.5.degree. in regard to the substrate after ozone
irradiation, .theta.2=47.degree. in regard to the binder which used
polyvinyl alcohol, and .theta.3=67.degree. in regard to the wall
member by the compound material of gum arabic and gelatin. Note
that the binder and the wall member are measured when they are
respectively in the film state.
[0083] As shown in FIG. 3B, under the conditions described above,
as the binder 36 entwined around the microcapsules 35 attempts to
spread along the common electrode substrate 10, a surface tension
of the binder 36 causes to expand the microcapsules 35 themselves
(in the direction of arrow). Expanded microcapsules 35 are fixed on
the common electrode substrate 10 in a single layer (one by one
without overlaying in the thickness direction) in the stone wall
shape or the tile shape arrayed in a row vertically and
horizontally with no mutual gaps.
[0084] In this manner, the electrophoretic display sheet is
manufactured.
[0085] As shown in FIG. 2D, in process D, an adhesive 41 for
sticking the pixel electrode substrate 20 arranged opposite to the
common electrode substrate 10 is coated on the electrophoretic
layer 30 which was made into a film. In coating the adhesive, it
may be on the entire surface or periphery of the electrophoretic
layer 30, so long as the microcapsules 35 are sealed with the pixel
electrode substrate 20 and the common electrode substrate 10.
[0086] Finally, as shown in FIG. 2E, in process E, the pixel
electrode substrate 20 made by a separate process is glued to the
common electrode substrate 10 such that its electrode side surface
joins the adhesive 41, thereby sealing and fixing the
electrophoretic layer 30 which was made into a film. In this way,
an electrophoretic display using the electrophoretic display sheet
is obtained.
[0087] FIG. 4 shows the electrophoretic layer 30 in the film state
obtained as a result of process C. In this manner, by pressuring
the opposite substrates, without pushing and expanding the
microcapsules 35, when the binder 36 entined around the
microcapsules 35 spreads on the substrate, the microcapsules
themselves expand due to the surface tension of the binder 36. The
electrophoretic layer 30 can be made into a film on the common
electrode substrate 10 with the microcapsules 35 in the state of
being packed without a gap in the stone wall shape or the tile
shape.
[0088] The electrophoretic display 1 as referenced above can be
built into various electric apparatus. Electric apparatus according
to the invention equipped with the electrophoretic display will be
described as follows.
[0089] FIGS. 6 and 7 are diagrams showing examples of electronic
equipment to which the above-referenced electrophoretic display is
applicable. FIG. 6A is an example of application to a mobile phone.
The mobile phone 230 comprises an antenna part 231, a voice output
unit 232, a voice input unit 233, an operating unit 234, and the
electrophoretic display 1 of the invention. In this way, the
electrophoretic display according to the invention can be used as a
display.
[0090] FIG. 6B is an example of application to a portable
electronic book, and an electronic book 250 consists of a dial
operating part 251, a pushbutton operating part 252, and the
electrophoretic display 1 according to the invention.
[0091] FIG. 7A is an example of application to a still image
display, and a still image display 300 is provided with the
electrophoretic display 1 according to the invention. Note that the
still image display according to the invention is likewise
applicable to a monitor unit used in a personal computer and the
like.
[0092] FIG. 7B is an example of application to a roll-up type still
image display, and the roll-up type still image display 310 has the
electrophoretic display according to the invention.
[0093] As described above, based on the illustrated embodiments,
description has been made of the electrophoretic sheet, the
electrophoretic display, the manufacturing process of the
electrophoretic display, and the electric apparatus using the
electrophoretic display according to the invention. While the
invention is not limited to these working examples, the
constitution of each part or unit can be replaced with any
constitution having like functions. Further, any other constituent
element may be added to the invention.
[0094] Furthermore, the invention may be a combination of more than
any two constitutions (characteristics) out of each embodiment
referenced above.
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